/*
  Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
  2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017,
  2018, 2019, 2020, 2021 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* Simple minded read-ahead/write-behind subroutines for tftp user and
   server.  Written originally with multiple buffers in mind, but current
   implementation has two buffer logic wired in.

   Todo:  add some sort of final error check so when the write-buffer
   is finally flushed, the caller can detect if the disk filled up
   (or had an i/o error) and return a nak to the other side.

			Jim Guyton 10/85
 */

#include <config.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#ifdef HAVE_SYS_FILIO_H
# include <sys/filio.h>
#endif
#include <netinet/in.h>
#include <arpa/tftp.h>

#include <stdio.h>
#include <unistd.h>

#include "tftpsubs.h"

/* Some systems define PKTSIZE in <arpa/tftp.h>.  */
#ifndef PKTSIZE
#define PKTSIZE SEGSIZE+4	/* should be moved to tftp.h */
#endif

struct bf
{
  int counter;			/* size of data in buffer, or flag */
  char buf[PKTSIZE];		/* room for data packet */
} bfs[2];

				/* Values for bf.counter  */
#define BF_ALLOC -3		/* alloc'd but not yet filled */
#define BF_FREE  -2		/* free */
/* [-1 .. SEGSIZE] = size of data in the data buffer */

static int nextone;		/* index of next buffer to use */
static int current;		/* index of buffer in use */

				/* control flags for crlf conversions */
int newline = 0;		/* fillbuf: in middle of newline expansion */
int prevchar = -1;		/* putbuf: previous char (cr check) */

static struct tftphdr *rw_init (int);

struct tftphdr *
w_init (void)
{
  return rw_init (0);
}				/* write-behind */
struct tftphdr *
r_init (void)
{
  return rw_init (1);
}				/* read-ahead */

/* init for either read-ahead or write-behind */
/* zero for write-behind, one for read-head */
static struct tftphdr *
rw_init (int x)
{
  newline = 0;			/* init crlf flag */
  prevchar = -1;
  bfs[0].counter = BF_ALLOC;	/* pass out the first buffer */
  current = 0;
  bfs[1].counter = BF_FREE;
  nextone = x;			/* ahead or behind? */
  return (struct tftphdr *) bfs[0].buf;
}


/* Have emptied current buffer by sending to net and getting ack.
   Free it and return next buffer filled with data.
 */
/* if true, convert to ascii */
/* file opened for read */
int
readit (FILE * file, struct tftphdr **dpp, int convert)
{
  struct bf *b;

  bfs[current].counter = BF_FREE;	/* free old one */
  current = !current;		/* "incr" current */

  b = &bfs[current];		/* look at new buffer */
  if (b->counter == BF_FREE)	/* if it's empty */
    read_ahead (file, convert);	/* fill it */
  /*      assert(b->counter != BF_FREE); *//* check */
  *dpp = (struct tftphdr *) b->buf;	/* set caller's ptr */
  return b->counter;
}

/*
 * fill the input buffer, doing ascii conversions if requested
 * conversions are  lf -> cr,lf  and cr -> cr, nul
 */
/*	FILE *file;  file opened for read */
/*	int convert;  if true, convert to ascii */
void
read_ahead (FILE * file, int convert)
{
  register int i;
  register char *p;
  register int c;
  struct bf *b;
  struct tftphdr *dp;

  b = &bfs[nextone];		/* look at "next" buffer */
  if (b->counter != BF_FREE)	/* nop if not free */
    return;
  nextone = !nextone;		/* "incr" next buffer ptr */

  dp = (struct tftphdr *) b->buf;

  if (convert == 0)
    {
      b->counter = read (fileno (file), dp->th_data, SEGSIZE);
      return;
    }

  p = dp->th_data;
  for (i = 0; i < SEGSIZE; i++)
    {
      if (newline)
	{
	  if (prevchar == '\n')
	    c = '\n';		/* lf to cr,lf */
	  else
	    c = '\0';		/* cr to cr,nul */
	  newline = 0;
	}
      else
	{
	  c = getc (file);
	  if (c == EOF)
	    break;
	  if (c == '\n' || c == '\r')
	    {
	      prevchar = c;
	      c = '\r';
	      newline = 1;
	    }
	}
      *p++ = c;
    }
  b->counter = (int) (p - dp->th_data);
}

/* Update count associated with the buffer, get new buffer
   from the queue.  Calls write_behind only if next buffer not
   available.
 */
int
writeit (FILE * file, struct tftphdr **dpp, int ct, int convert)
{
  bfs[current].counter = ct;	/* set size of data to write */
  current = !current;		/* switch to other buffer */
  if (bfs[current].counter != BF_FREE)	/* if not free */
    write_behind (file, convert);	/* flush it */
  bfs[current].counter = BF_ALLOC;	/* mark as alloc'd */
  *dpp = (struct tftphdr *) bfs[current].buf;
  return ct;			/* this is a lie of course */
}

/*
 * Output a buffer to a file, converting from netascii if requested.
 * CR,NUL -> CR  and CR,LF => LF.
 * Note spec is undefined if we get CR as last byte of file or a
 * CR followed by anything else.  In this case we leave it alone.
 */
int
write_behind (FILE * file, int convert)
{
  char *buf;
  int count;
  register int ct;
  register char *p;
  register int c;		/* current character */
  struct bf *b;
  struct tftphdr *dp;

  b = &bfs[nextone];
  if (b->counter < -1)		/* anything to flush? */
    return 0;			/* just nop if nothing to do */

  count = b->counter;		/* remember byte count */
  b->counter = BF_FREE;		/* reset flag */
  dp = (struct tftphdr *) b->buf;
  nextone = !nextone;		/* incr for next time */
  buf = dp->th_data;

  if (count <= 0)
    return -1;			/* nak logic? */

  if (convert == 0)
    return write (fileno (file), buf, count);

  p = buf;
  ct = count;
  while (ct--)
    {				/* loop over the buffer */
      c = *p++;			/* pick up a character */
      if (prevchar == '\r')
	{			/* if prev char was cr */
	  if (c == '\n')	/* if have cr,lf then just */
	    fseeko (file, -1, 1);	/* smash lf on top of the cr */
	  else if (c == '\0')	/* if have cr,nul then */
	    goto skipit;	/* just skip over the putc */
	  /* else just fall through and allow it */
	}
      putc (c, file);
    skipit:
      prevchar = c;
    }
  return count;
}


/* When an error has occurred, it is possible that the two sides
 * are out of synch.  Ie: that what I think is the other side's
 * response to packet N is really their response to packet N-1.
 *
 * So, to try to prevent that, we flush all the input queued up
 * for us on the network connection on our host.
 *
 * We return the number of packets we flushed (mostly for reporting
 * when trace is active).
 */

/*int	f;socket to flush */
int
synchnet (int f)
{
  int i, j = 0;
  char rbuf[PKTSIZE];
  struct sockaddr_storage from;
  socklen_t fromlen;

  while (1)
    {
      ioctl (f, FIONREAD, &i);
      if (i)
	{
	  j++;
	  fromlen = sizeof from;
	  recvfrom (f, rbuf, sizeof (rbuf), 0,
		    (struct sockaddr *) &from, &fromlen);
	}
      else
	{
	  return (j);
	}
    }
}
